Straferunning

Straferunning is running forward and moving sideways (strafing) at the same time, which results in moving faster than is possible in either direction alone. One of the advantages is being able to jump farther than is otherwise possible.

There are two straferunning speeds: SR40 and SR50. The 40 and 50 refer to the sideways speed. The run-forward speed is 50 in either case.

SR40 (to the right) may be activated using Run, Forward, and Strafe Right (shift, up arrow, and period in the default keyboard arrangement). It may also be activated using Run, Forward, Strafe On, and Turn Right (shift, up arrow, alt, right arrow). SR40 results in a speed of &radic;(40&sup2; + 50&sup2;) = 64 (128% of normal run-forward speed) at an angle of arctan(40/50) = 38.7 degrees (to the right of directly forward). (N.B. The Doom engine does not perform any special calculations for this. The results are simply due to solving the triangle formed when the player moves forward 50 and sideways 40 in a single time unit.) The maximum jump distance (between platforms at equal height) is 181 units.

SR50 (to the right) may be activated using Run, Forward, Strafe Right, Strafe On, and Turn Right (shift, up arrow, period, alt, and right arrow in the default keyboard arrangement). It results in a speed of &radic;(50&sup2; + 50&sup2;) = 70.7 (141% of normal run-forward speed) at an angle of arctan(50/50) = 45 degrees. The maximum jump distance (between platforms at equal height) is 196 units. SR50 is the fastest speed obtainable (except for wallrunning), but it is awkward to activate and it is not possible to turn while in SR50 mode.

SR50 is possible because the Doom engine adds multiple strafe inputs together and limits the resulting value to 50. A single strafe input produces a speed of 40 (assuming the sprint key is held), so two inputs must be used to reach the maximum speed. Mouse-strafing inputs can go all the way up to 50, so SR50 can be achieved with mouse alone.

The use of mouse buttons and customized keyboard arrangements will facilitate straferunning: see Controls.

Trivia
According to John Romero, straferunning did not come about until almost a year after Doom's release, and was unanticipated in the design of the original levels. (See .)